The last time the NASA budget was this low as a percentage of the federal budget was 1961. It's really bad that this isn't well understood on a site like HN. If we can't justify it here...
I imagine many of the most expensive years were due to the space race with Russia. Basically, a side-effect of the cold war. Can that really be taken to represent the peak of human interest for the sake of science alone?
Why is a percentage a relevant measurement here? I think you would just want to measure budget compared YoY adjusted for inflation. The reason it doesn't make sense is that the US budget doesn't need to be balanced. It's not like spending a ton more on subsidies for something new (e.g. renewables/electric cars/healthcare) means that NASA lost money).
You have managed to derail the conversation away from the science and imply that America is falling behind in space. Claiming the US should be even more dominant in space seems odd given the lopsided reality. Maybe you are invoking American exceptionalism.
I'm not sure why you're looking at space exploration as a competition where we want to dominate. It's not a competition. We should welcome everyone. Even if no one else participates we should still increase our effort, not reduce it. There's so much more to learn.
As I mentioned earlier, this article explains it much better than I could:
https://en.m.wikipedia.org/wiki/Budget_of_NASA#/media/File:N...